Protecting device for electric detonators



Oct. 12 1'926. 1,603,048 V H. L. GRANT PROTECTING DEVICE FOR ELECTRICDBTONATORS Filed Nov. 20, 1925 awue/nfoz flarry l. Grant,

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HARRY L. GRANT, OF TAHZAQUA, PENNSYLVANIA, ASSIGNOR TO ATLAS EGW'DERCGIVL IANY, OF WILI/IINGTQN, BELAW'ARE, A CGRPDRATIQN 0F DELAXVARE.

PROTECTING DEVICE FOR ELECTRIC DETONATORS.

Application filed November 2'0, 1925. Serial No. 70,364.

This invention relates to a protecting device for electric detonators ofthe character of that shown in my copending application, Serial No.748,214, filed on November 6, 19%.

Like the device of the application referred to, the protecting device ofthe present in vention is intended to be applied to the lead-in wires ofelectrical detonators and to serve, while in position, to establish ashort circuit between the two lead-in wires, so that any stray currentsimposed upon the lead-in wires, outwardly of the point of application ofsaid device, may not find their way to the detonator and prematurelyexplode the same, and so that no difference of potential can be createdbetween the wires inwardly of the point of application of the deviceunder the influence of accidental or stray currents.

I am aware of the fact that it has been proposed to short circuit themain firing cable leading from the blasting machine. However, thatmethod is of utility only at the time of use. An important object of thepresent invention is to provide a structure which will be operative withrespect to the individual detonators, at all times between the time ofmanufacture of the detonator and until the same is actually eX- plodedon the job, the structure being of particular utility during the timethat the detonator is being transported and while it is being handledabout the work preliminary to the actual connection of its lead wires tothe main firing cable.

The present application is directed to the protection of a specific formof short circuiting shunt and method of applying the same to the lead-inwires of the individual blasting caps, preferably with its inner endabutting and resting firmly against the terminal end of the usualinsulation of the detonators. In the provision of a structure of thischaracter, which is used only once and then thrown away, it is ofimportance that it be of a simple and inexpensive nature and one adaptedto be applied rapidly by automatic machinery. l Vith this end in view, Ihave devised the shunt shown in the accompanying drawing wherein:

Fig. 1 18 a perspective vlew of the short circuiting shunt the same,

Fig. 2 is a side elevation of a detonator with the shunt appliedthereto,

Fig. 3 is an end view of the shunt after being applied, and

Fig. 4 is a longitudinal sectional view through the shunt, afterapplication.

Like numerals designate corresponding parts in all of the figures of thedrawing.

Referring to the drawing, 5 designates the conventional electricdetonator and 6 and 7 designate the usual lead-in wires of saiddetonator.

In the ordinary use of the *detonator the flow of current ofsutficientstrength past an igniting element 8, which connects the innerends of the wires 6 and 7, explodes the detonat'or. The lead-in wiresare insulated, as indicated at 9 and 10, for some distance from thedetonator and the ends of the leadin wires are left bare beyond thepoint where the insulation terminates, to adapt them for readyapplication to the firing cable, leading from a blasting machine.

To provide for the rapid and economical application of a shunt to thelead-in wires 6 and 7 of the detonator, I provide a tubular body 11 andthread the lead-in wires through this body and then compress said bodyfirmly about the wires and into the form of a block. The body 11 may beformed of lead, copper, aluminum or any other suitable conductivematerial and it is usually applied to the leadin wires in such mannerthat the inner end of the resultant block abuts snugly against the outerend of the insulation, 9 and 10, of the wires. It is not to beunderstood that the device is of utility only when actu ally touchingthe termination of the insu lation. It will give a very appreciablemeasure of protection even when spaced somewhat from the insulationbecause the influences which might bring about such difference inpotential between the lead wires as to explode the detonator, are notthose sought to be created by an intelligent human agency but only thosewhich might accidentally occur. Stray currents of such low E. M. F. asto escape ordinary notice constitute a marked source of danger and arerendered absolutely harmless by this prior to the application of saidwires do not touch each other. Thus great care 1D the positioning of thewires,

during the application of the body 11, is rendered unnecessary and theshort circuiting shunt may be applied rapidly and upon a commercialscale. The tubular shunts may be rapidly made by severing. them from along tube of the proper metal.

lVhen the short circuiting shunt is to be removed at the time of use ofthe detonator, it is stripped longitudinally from the wires 6 and 7.from the wires cleans and brightens them and insures a good electricalunion between said wires and the firing cables towhich they are to beattached. To facilitate the cleaning action 01 the shunt as it isstripped from the Wires, I cut the end of the tubular body 11 squarelyacross to render the contacting edges of said body, which engage thewires, as sharp as possible, so that in the stripping action they willexert a scraping The act of stripping the shunt effect upon the leadwires of the detonator.

It is understood that the invention is not limited to the preciseconstruction set forth but that it includes within its purview what everchanges fairly come Within either the terms or the spirit of theappended claims.

Having described my invention, what I claim is:

1. The combination with a detonator and its lead wires, said lead wireshaving their inner portions covered with insulating ma terial and theirouter portions left bare, of an electric shunt comprising a body ofconductive material of tubular form through which the bare portions ofthe wires have been threaded and which body has been compressed aboutsaid wires, with its inner ends abutting the outer ends of theinsulation.

2. A structure as recited in claim 1 Wherein the. outer end of the,tubular body is shaped to constitute a scraping edge when the shunt isstripped longitdinally from the- Wll'QS.

In testimony whereof he aiiines his s1gnature.

HARRY L. GRANT.

